Core body temperature of a congestive heart failure patient exhibits patterns of behavior under certain circumstances. For instance, the core temperature of a congestive heart failure patient tends to decrease during exercise, primarily due to the circulatory inadequacies associated with this condition. Shellock (J Appl Physiol 1985 February; 58(2): 400–8) studied core temperatures (pulmonary arterial blood), femoral vein, muscle, and skin temperatures in eight patients with severe heart failure performing maximal upright incremental bicycle exercise to 50 W. A normal group of four individuals was exercised for comparison. In the heart-failure patients, the core temperature was 36.95+/−0.37 degrees C. at rest, and decreased to 36.59+/−0.40 degrees C. at 25 W of exercise. At 50 W of exercise, the temperatures were 36.57+/−0.40 degrees C. In contrast, the resting core temperature in the normal subjects was 37.28+/−0.34 degrees C. At 25 W of exercise, the core temperature in the normal subjects was the same as the resting core temperature. At 50 W of exercise, the temperature of the normal subjects increased to 37.50+/−0.32 degrees C.
Currently, leads are used, for example, to measure a core temperature of a body where the thermal sensor is placed in the right ventricle to measure a mix of the blood temperature, as discussed in U.S. Pat. No. 4,688,573, issued on Aug. 25, 1987. However, the core temperature of a body, or blood which flows through the right ventricle, involves an average temperature of many locations. For instance, blood from within the right ventricle is blood collected from the brain, kidney, lymph system as well as other locations within the body, resulting in a temperature which is an average of all of these locations. Collecting readings of average temperatures such as the above may not provide accurate information regarding what is occurring only within the heart, or the effectiveness of the heart.
Accordingly, what is needed is a more accurate way to monitor the effectiveness of a heart.